Research shows that non-secretor mothers are less able to protect their babies from infection with the Norwalk virus (NV) through breastfeeding than secretor mothers (1). Breast milk contains many secreted carbohydrates, including the blood group antigens, however non-secretors lack the ability to secrete their blood group antigens in their breast milk and other fluids.

It is already known (2) that secretors of their blood group antigen are more at risk of contracting gastroenteritis from NV infection, except for individuals of blood group B (3), who are at less risk of developing symptoms.

The Norwalk virus is the main cause of gastroenteritis “food poisoning” infection of a non-bacterial source. NV has a ligand that attaches to the A and H antigens in the saliva and digestive tract of blood groups O, A and AB to take hold and infect the host, but only in secretors. A ligand is a molecule that binds to another chemical entity to form a larger complex, like the agglutination of blood group antigens by lectins.

Symptoms of NV infection are: nausea, vomiting, diarrhoea and stomach cramps. Infected people usually recover in 2 to 3 days without serious or long-term health effects.

The new research shows that the milk of secretor mothers inhibits the attachment of NV to the receptors in their baby, but non-secretor mothers lack this protective secretion. Therefore non-secretor mothers are less likely to contract gastroenteritis from NV, but their babies may be at higher risk than babies of breastfeeding secretor mothers.

Suggested ways to limit the spread of Norwalk virus include:

• Wash hands with soap and warm water after toilet visits and before preparing or eating food;

• Cook all shellfish thoroughly before eating;

• Wash raw vegetables before eating;

• Dispose of sewage, including soiled nappies, in a sanitary manner.

Read ‘Eat Right 4 Your Baby’ to learn about ways of looking after your child while pregnant and breastfeeding.